Anaerobic Reduction Process Characteristics and Microbial Community Analysis for Sulfate and Fe(Ⅱ) EDTA-NO/Fe(Ⅲ) EDTA

Abstract

Based on biological flue gas desulfurization technology (Bio-FGD) and chelating absorption-biological regeneration technology (BioDeNOx), simultaneous desulfurization and denitrification by biological methods combined with chelating absorption technology has been proposed in this study. This technique uses an alkaline absorption liquid with Fe(Ⅱ) EDTA to absorb the SO2 and NO in the flue gas. In this study, an attempt is made to simultaneously remove sulfate (SO42-) and Fe(Ⅱ) EDTA-NO/Fe(Ⅲ) EDTA, which are the SO2 and NO absorption byproducts in an anaerobic reactor. The results indicate that average removal efficiencies for SO42- and Fe(Ⅱ) EDTA-NO of 95.16% and 96.61%, respectively, were achieved when the hydraulic residence time (HRT) and pH were controlled at 16 h and 7.0. The reduction products of SO42- were mainly in the form of S2- in the liquid phase and hydrogen sulfide (H2S) in the gas phase, while the reduction products of Fe(Ⅱ) EDTA-NO was N2. The reduction of Fe(Ⅲ) EDTA could be achieved at all stages of the operation, however, the reduction rate decreases with a reduction in the HRT. In the fifth stage, the main sulfate-reducing bacteria (SRB) in the reactor was Desulfomicrobium, a heterotrophic denitrifying bacteria, Pseudomonas, and two types of sulfur autotrophic denitrifying bacteria, Sulfurimonas and Sulfurovum, which coexisted. Two genera of bacteria that can also reduce sulfur, Thermovirga and Mesotoga, were also identified in the reactor.